I believe the best way to gain self confidence if you stutter is to encapsulate your stutter in with your confidence. A lot of people think of confidence of "how can I not stutter" but being able to stutter and be confidence, shows 10x more true confidence. It really all just comes down to your relationship with your stutter. If you are viewing it negatively then obviously that wouldn't help. You will be constantly trying to avoid it, causing you to be in your head, causing you to be anxious, scripted, and monotone. Which leads to you stuttering even more and fulfilling that prophecy again and again. Have you worked on changing your relationship with your stutter?